Valve construction

ABSTRACT

A valve seat means defines an opening for receiving a valve means and has a seating surface formed thereon. A chamfer is formed on the valve seat means between the opening and seating surface thereof. A valve means includes a sealing surface for engaging the seating surface of the valve means, and a spring means engages the valve means to urge the surfaces into sealing engagement. The valve means includes a poppet portion having a tapered surface which is in communication with a substantially straight cylindrical shoulder. This shoulder fits relatively closely within the opening in the valve seat means and is disposed adjacent the chamfer on the valve seat means. The shoulder on the valve means has a greater dimension in a direction extending substantially parallel with the direction of movement of the valve means than does the chamfer on the valve seat means.

United States Patent 72 Inventor Lawrence A. Botkin 2,583,169 1 1952Funkhouser 137 4935 Omaha, Nebr. 2,601,563 6/1952 Selwyn 137/540 [21]Appl. No. 792,294 2,691,387 10/1954 Strauss... 137/541 X [22] Filed Jan.21, 1969 2,869,569 1/1959 Kimmell 1. 137/469 X [45] Patented Sept. 14,1971 FOREIGN PATENTS [731 Asslgnee g" D.17,613 12/1955 Germany 137/4935e 829,931 3/1960 Great Britain. 137/541 7 497,472 12/1938 Great Britain137/540 [54] VALVE CONSTRUCTION Primary Examiner-M. Cary Nelson 8Claims, 4 Drawing Figs. Assistant Examiner-Robert .1. Miller 52 us. (:1.1 137/493.4, Bumm 137/543.17 [51] lltt. Cl. Fl6k 17/18 ABSTRACT: Avalve Seat means fi an opening f [50] Flew Msearch" 37/4934 receiving avalve means and has a seating surface formed thereon. A chamfer isformed on the valve seat means between the opening and seating surfacethereof. A valve [56] References Cited means includes a sealing surfacefor engaging the seating surface of the valve means, and a spring meansengages the valve UNITED STATES PATENTS means to urge the surfaces intosealing engagement. The valve 1,760,391 5/1930 Williams et al. 251/122means includes a poppet portion having a tapered surface 2,724,406 11/1955 Murray 137/491 which is in communication with a substantiallystraight cylin- 3,155,366 1 1/1964 Rasmussen 137/490 X drical shoulder.This shoulder fits relatively closely within the 432,140 7/1890 Kilborn137/469 4 opening in the valve seat means and is disposed adjacent the2,072,271 3/1937 Meadows 137/541 chamfer on the valve seat means. Theshoulder on the valve 2,162,743 6/1939 Norbom l37/493.4 means has agreater dimension in a direction extending sub- 2,320,339 6/1943 Buttner137/540 X stantially parallel with the direction of movement of thevalve 2,547,862 4/1951 Gilmore [37/469 X a means than does the chamferon the valve seat means.

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11 as a? (1 156 152 I50 154 96 4 86 PATENTEDSEPMISYI 3.604450 SHEEI 1[1P2 FIG. 3

mvlzu'ron LAWRENCE A. BOTKIN B; Mum" ATTORNEYS VALVE CONSTRUCTIONBACKGROUND OF THE INVENTION The present invention relates to a valveconstruction, and more particularly to a valve construction which isparticularly suited for use in relief valves and to provide properoperation thereof. This type of relief valve is especially suited foruse with tank containers and chemical trailers of the like.

In conventional pressure relief valves for handling gases or vapors,proper operation is generally assured by employing a diffuser ringarrangement outside of'the disc assembly. This type of constructionrequires close guiding of the poppet assembly within the seat opening ofthe valve. Such valves are disadvantageous since they are relativelyexpensive in construction and difficult to maintain. Additionally, thistype of valve is likely to clog when handling viscose materials and isthereby prone to failure due to contamination.

SUMMARY OF THE INVENTION In the present invention, the valve seat meanshas an opening for receiving the valve and includes a seating surface. Achamfer is formed between the opening and the seating surface and has apredetermined dimension parallel with the axis of movement of the valvemeans. The valve means itself includes a sealing surface for engagingthe seating surface of the valve seat means, and spring means isoperatively connected with the valve means for urging the two surfacesinto sealing engagement with one another.

The valve means also includes a poppet portion having a tapered surfacewhich joins with a substantially straight cylindrical shoulder fittingclosely within the opening defined in the valve seat means and beingdisposed adjacent to the chamfer on the valve seat means when the valvemeans is in sealing position. The shoulder has a predetermined dimensionin a direction extending substantially parallel with the axis ofmovement of the valve means which is substantially greater than that ofthe chamfer, and is preferably at least about two times as great.

The tapered surface on the poppet portion and the fact that the shoulderformed on the poppet portion fits closely within the opening formed inthe valve seat means with only very slight clearance with respectthereto assures that the valve means is automatically centered withinthe valve seat means when the valve means moves to its sealing position.This tapered surface on the poppet portion is preferably substantiallyfrustoconical and helps to direct the flow of discharge gases from thevalve assembly so as to obtain optimum lift characteristics under mostconditions.

The spring means comprises a stable spring having a relatively largediameter and short length whereby mechanical guiding of the spring isunnecessary. Additional mechanical guiding of the valve means and poppetportion is not required, and accordingly, the valve of the presentinvention does not have a tendency to clog when handling viscosematerials.

Since the shoulder on the poppet portion extends longitudinallysubstantially beyond the chamfer formed on the valve seat when the valvemeans is in sealing position, the valve means is accurately centered andheld in proper sealing relationship with respect to the associated valveseat means.

Accurate centering of the valve means is important to provide the mosteffective seal at low pressures. When a resilient sealing surface isprovided on the valve means, the valve seat may be provided with asloping surface and a flat thereon.

The arrangement of the present invention in actual tests has proved tohold bubbletight up to the maximum practical percentage of the setpressure of the valve. The valve also successfully repeats sealingoperation thereof at a given pressure due to the accurate centering ofthe valve means with respect to both the valve seat means and theassociated spring means. Misalignment of the valve means either with theseat means or the spring means results in the spring force beingimproperly centered thereby allowing the valve means to tip and relieveat erratic pressure settings.

It is also most important when considering relief valves to provide avalve which will achieve a rated flow capacity when the pressure is 20percent in excess of'the set pressure. The arrangement of the presentinvention provides a'substantial flow rating at a pressure 20 percentgreater than the set pressure. In

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical section through afirst embodiment of a valve according to the present invention;

FIG. 2 is an enlarged view of a portion of the structure shown in FIG.1;

FIG. 3 is a vertical section through an assembly illustrating a pair ofvalves disposed in side-by-side relationship; and

FIG. 4 is a vertical section through a modified valve assembly accordingto the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawingswherein like reference characters designate corresponding partsthroughout the several views, a first embodiment of the presentinvention is illustrated in FIGS. 1 and 2. A flange member 10 may beretained in its mounting by a suitable fusible material which may forexample fuse at a temperature of about 250 F. A valve seat means isformed in flange member 10, the valve seat means including a pair ofseating surfaces 12 and 14 which are tapered at an angle ofapproximately 5 with respect to the opposite faces of flange member 10.

As seen most clearly in FIG. 2, sloping surfaces 12 and 14 are providedwith flats 16 and 18 thereon which are disposed substantially parallelwith the opposite faces of flange member 10. Chamfers 20 and 22 areformed between the seating surfaces and a substantially straightcylindricalsurface 24 defining an opening for receiving the valve meanshereinafter described.

In a typical example wherein the central opening defined by surface 24may have a diameter of approximately L250 inches, the flats 16 and 18may have a dimensionextending parallel with the opposite surfaces offlange member 10 of approximately one thirty-second inch. The chamfers20'and 22 have a predetermined longitudinal dimension extendingsubstantially parallel with the axis of movement of the associated valvemeans, or in other words parallel with surface 24 of approximately onesixty-fourth inch.

The valve means includes an elongated substantially cylindrical shaft orstem 30 having external threads formed thereon. A poppet portion 32 hasa central threaded bore 34 formed therethrough, this poppet portionbeing threaded onto the stem as illustrated and being fixed in place bya seal weld 36 extending around the stem.

The poppet portion includes a part 40 having a tapered outer surface ofgenerally frustoconical configuration, this tapered surface being incommunication with a shoulder 42 which defines a substantially straightcylindrical surface. This surface 42 is disposed adjacent the chamfer 20when the valve is in sealing position. Shoulder 42 fits closely withinthe opening defined by surface 24 and has only a slight clearance withrespect thereto. In the aforementioned example, the clearance betweenthe shoulder 40 and surface 42 may be onthe'order of 0.005 to 0.015inch. Additionally, this shoulder has a longitudinal dimension extendingsubstantially parallel with the axis of movement of the valve means, orin other words parallel with the axis of stem 30, which is greater thanthe corresponding dimension of the-chamfer 20. In the aforementionedexample, this longitudinal dimension of shoulder 42 is approximately onethirty-second inch and accordingly is at least about two times as greatas the corresponding dimension of chamfer 20. Chamfer 22 has alongitudinal dimension similar to that of chamfer 20.

The upper surface 44 of the poppet portion engages the undersurface of aresilient gasket member 50. This gasket member may be formed of anysuitable resilient sealing substance such as rubber, plastic or the likeas desired. Gasket 50 is of annular configuration and includes a centralhole 52 receiving the stem 30. The gasket member is received within acomplementary recess formed in the undersurface of gasket retainer 54.Retainer 54 has a central threaded bore 56 formed therethrough whichreceives stem 30, and the gasket retainer is held in the operativeposition illustrated by a cotter pin 60 extending through suitablealigned holes formed in the gasket retainer and stem.

A spring retainer 62 is provided with a central threaded bore 64 whichreceives stem 30 of the valve means, the spring retainer being retainedin the operative position illustrated by a cotter pin 66 extendingthrough suitable holes provided in spring retainer 62 and a slot 68provided in he end of the valve stem.

A stable spring 70 is interposed between the spring retainer 62 and thesurface 14 of the valve seat means for normally urging the valve meansinto the sealing position illustrated wherein the sealing surface formedon the underside of gasket 50 is in engagement with the seating of thevalve seat means. The stable spring has a relatively large diameter anda short length so that close mechanical guiding of the spring isunnecessary. In a typical example as discussed hereinabove, the springmay comprise a 41-inch stainless steel spring having an outer diameterof l inches and a free height of 3 A inches.

Referring now to FIG. 3 of the drawings, the valve construction of thepresent invention is illustrated as it may be employed in a vacuum ventassembly. In this construction, the valve means aforedescribed isemployed at the left-hand portion of the figure and has been given thesame reference numerals. The valve may serve as a relief valve whereingas may be exhausted from beneath the flange to a point thereabove. Atthe right-hand side of the figure, a valve construction according to thepresent invention is illustrated wherein similar parts have been giventhe same reference numerals primed. This valve means at the right-handside of this figure serves as a vacuum vent, and it will be noted thatthe position of the vacuum vent valve means is inverted from that of thepressure relief valve means. It is accordingly apparent that the valvemeans may be readily inverted for use at either side of an associatedvalve seat means and will operate equally as well in either position.

Referring now to FIG. 4 of the drawings, a modified form of theinvention is illustrated. A swivel base 80 is provided with internalthreads 82 for receiving a suitable threaded member. A gasket 84 is alsoprovided for sealing engagement with the upper end of the associatedmember. A ring member 86 is secured to a base member 88. A plurality ofangle clips 90 are secured as by welding to the outer surface of basemember 88 and are preferably disposed at equally spaced intervalstherearound. The angle clips may be four in number and disposed at 90intervals with respect to one another.

A hole 92 is drilled through the wall of base member 88 at a pointsubstantially midway between a pair of adjacent angle clips 90 and anipple 94 is secured in this hole as by welding and the like. The outerend of the nipple is threaded for connection with a suitable means.

The upper end of base member 88 is provided with a valve seat means 100which is of similar construction to the valve seat means as shown inFIG. 2 except that the upper surface thereof does not slope as does theupper surface 12 of the aforementioned valve seat means. In other words,valve seat means 100 defined at the upper end of base member 88 includesa substantially flat surface extending in a plane perpendicular to themovement of the valve means. An opening for receiving the valve means isdefined by surface 102 which is a substantially straight cylindricalsurface as is the surface 24 previously described. A chamfer is providedbetween the seating surface and the opening as in the previouslydescribed embodiment.

In this modification, the valve means includes a poppet portion thelower part of which defines a tapered outer surface 112 which issubstantially frustoconical in configuration. This tapered surface joinswith a shoulder 114 corresponding to the shoulder 42 previouslydescribed and which is a substantially straight cylindrical surface. Asin the previously described modification, the shoulder 114 has adimension extending substantially parallel with the axis of movement ofthe valve means which is at least approximately two times as great asthe corresponding dimension of the chamfer formed on the cooperatingvalve seat means.

As mentioned previously, the frustoconical configuration of the lowerpart of the poppet portion helps direct the flow of discharge gases toobtain the best lift characteristics under most conditions. In addition,the poppet portion is provided with a further tapered surface which isalso substantially frustoconical and which is disposed radiallyoutwardly of the sealing surface 122 formed thereon which cooperateswith the seating surface formed on the associated valve seat means. Thisadditional tapered surface 120 further improves the discharge capabilityof the valve. The outer part of the poppet portion includes a dependingskirt portion 124.

A substantially cylindrical pipe nipple is rigidly secured as by weldingto the spaced angle clips 90, and is provided with external threadsthereon. A generally cylindrical half coupling 132 is provided withinternal threads and is threaded onto member 130 as illustrated. Member132 is inturn rigidly connected with a disclike cap 134 as by welding orby use of a suitable fusible metal element indicated at 136.

Poppet portion 110 is provided with a central hole formed therethrough,this central hole being counterbored to provide a series of shoulders. Astable compression spring 142 has the upper end thereof seated within anannular groove 144 formed in the undersurface of cap 134. The lower endof spring 142 is seated upon a shoulder 146 formed on poppet portion 110for urging the poppet portion downwardly into the sealing positionillustrated.

A valve means is in turn mounted within the central hole provided withinpoppet portion 110. This valve means includes a poppet portion 150having a tapered outer surface 152 corresponding to the tapered surface40 of the previously described modification. The undersurface 154 of thevalve means comprises a sealing surface for engaging a seating surface156 formed at the bottom of poppet portion 110 is surroundingrelationship to the central hole formed therethrough. The constructionof the cooperating seat portion and poppet portions are identical withthat aforedescribed in connection with FIG. 1 in that the seat portionincludes a chamfer formed between the seating surface thereof and thesurface defining the central opening for receiving the valve means. Thepoppet portion includes the substantially frustoconical tapered surfacejoining with a shoulder which is a substantially right cylindricalsurface, and the same relative dimensions are employed for ensuringaccurate centering of the last-mentioned valve means within theassociated valve seat means on poppet portion 110.

A threaded stem 160 extends from poppet portion 150. A spring retainer162 is mounted on the outer end of the threaded stem portion and issecured in place by cotter pin 164 extending through suitable holesprovided in the spring retainer and a slot 166 formed in the end of thestem. A stable spring 170 is interposed between the spring retainer 162and a shoulder 172 formed on poppet portion 1 10.

It is readily apparent that the valve mans supported within poppetportion 110 is quite similar in its construction and operation as thatdescribed in connection with FIG. 1, and in fact the very same valvemeans as shown in FIG. 1 can also be supported within the poppet portion110 of the embodiment shown in FIG. 4 of the drawings.

A sealing clip 180 is secured as by welding to member 132 and extendsradially outwardly thereof. A seal wire 182 extends through a hole 184provided in the sealing clip and extends around one of the angle clips90.

in the modification illustrated in FIG. 4, the valve incorporates ametal-to-metal seat. The arrangement shown in FIG. 4 may also beemployed in a vacuum vent assembly, poppet portion 110 comprising thepressure relief valve means, and poppet portion 150 comprising thevacuum vent valve means.

As this invention may be embodied in several forms without departingfrom the spirit or essential characteristics thereof, the presentembodiment is therefore illustrative and not restrictive, and since thescope of the invention is defined by the appended claims, all changesthat fall within the metes and bounds of the claims or that form theirfunctional as well as conjointly cooperative equivalents are thereforeintended to be embraced by those claims.

What is claimed is:

1. A valve construction comprising valve seat means, said valve seatmeans defining an opening for receiving a valve, said valve seat meansalso including a seating surface, said valve seat means having a chamferdisposed between said opening and said seating surface, valve meansincluding a sealing surface for engaging said seating surface to providea seal, said valve means including a poppet portion, spring meansoperatively connected with said valve means to cause said sealingsurface to engage said seating surface, said poppet portion including atapered surface movable within said opening for centering the valvemeans, said poppet portion also including a shoulder adjacent saidtapered surface, said shoulder when the valve is in sealing positionbeing disposed within said opening and adjacent said chamfer, saidopening defined by said valve seat means being formed by a substantiallystraight cylindrical surface, said shoulder comprising a substantiallystraight cylindrical surface fitting relatively closely within saidopening with only a slight clearance between said two substantiallystraight cylindrical surfaces, said chamber having a predetermineddimension in a direction parallel with the axis of movement of saidvalve means, said shoulder having a predetermined dimension in adirection parallel with the axis of said valve means which is at leastabout two times as great as said dimension of the chamfer, said taperedpart of the poppet portion being substantially frustoconical inconfiguration, said valve means including an elongated valve stem, saidpoppet portion being fixedly supported on said valve stem, and a springretainer means supported on said valve stem and engaging said springmeans.

2. A valve construction comprising valve seat means, said valve seatmeans defining an opening for receiving a valve, said valve seat meansalso including a seating surface, said valve seat means having a chamferdisposed between said opening and said seating surface, valve meansincluding a sealing surface for engaging said seating surface to providea seal, said valve means including a poppet portion, spring meansoperatively connected with said valve means to cause said sealingsurface to engage said seating surface, said poppet portion including atapered surface movable within said opening for centering the valvemeans, said poppet portion also including a shoulder adjacent saidtapered surface, said shoulder when the valve is in sealing positionbeing disposed within said opening and adjacent said chamfer, saidopening defined by said valve seat means being formed by a substantiallystraight cylindrical surface, said shoulder comprising a substantiallystraight cylindrical surface fitting relatively closely within saidopening with only a slight clearance between said two substantiallystraight cylindrical surfaces, said chamfer having a predetermineddimension in a direction parallel with the axis of movement of saidvalve means, said shoulder having a predetermined dimension in adirection parallel with the axis of said valve means which is at leastabout two times as great as said dimension of the chamfer, said taperedpart of the poppet portion being substantially frustoconical inconfiguration, a second valve means having a second poppet portion and asecond sealing surface, said second poppet portion including a taperedsurface for centering the second valve means, a

second valve seat means including a second seating surface for engagingsaid second sealing surface to provide a seal therewith, saidfirst-mentioned sealing surface being formed on said second valve means,said first-mentioned valve means being carried by said second valvemeans, said second poppet portion having a central opening formedtherethrough, said opening receiving said first-mentioned valve means,spring means operatively connected with said second valve means, saidspring means being received within said central opening.

3. A valve construction comprising valve seat means, said valve seatmeans defining an opening for receiving a valve, said valve seat meansalso including a seating surface, said valve seat means having a chamferdisposed between said opening and said seating surface, valve meansincluding a sealing surface for engaging said seating surface to providea seal, said valve means including a poppet portion, spring meansoperatively connected with said valve means to cause said sealingsurface to engage said seating surface, said poppet portion including atapered surface movable within said opening for centering the valvemeans, said poppet portion also including a shoulder adjacent saidtapered surface, said shoulder when the valve is in sealing positionbeing disposed within said opening and adjacent said chamfer, secondvalve means having a second poppet portion and a second sealing surface,said second poppet portion including a tapered surface for centering thesecond valve means, a second valve seat means including a second seatingsurface for engaging said second sealing surface to provide a sealtherewith, said first-mentioned seating surface being formed on saidsecond valve means, said first-mentioned valve means being carried bysaid second valve means, said second poppet portion including a taperedsurface extending to a point adjacent said second sealing surface andlaterally inwardly thereof, said second poppet portion having a centralopening formed therethrough, said opening receiving said first-mentionedvalve means, spring means operatively connected with said second valvemeans, said spring means being received within said central opening.

4. Apparatus as defined in claim 1 wherein said spring means comprises astable spring.

5. Apparatus as defined in claim 1 wherein the seating surface on saidvalve seat means slopes relative to a plane extending perpendicular tothe axis of movement of said valve means.

6. Apparatus as defined in claim 5 wherein said seating surface includesa flat formed thereon adjacent said chamfer.

7. Apparatus as defined in claim 1 wherein said sealing surface on thevalve means comprises a gasket, and gasket retainer means supported onsaid valve stem and engaging said gasket for holding the gasket inplace.

8. Apparatus as defined in claim 3 wherein said second poppet portionincludes a second tapered surface formed adjacent to and laterallyoutwardly of said sealing surface.

1. A valve construction comprising valve seat means, said valve seat means defining an opening for receiving a valve, said valve seat means also including a seating surface, said valve seat means having a chamfer disposed between said opening and said seating surface, valve means including a sealing surface for engaging said seating surface to provide a seal, said valve means including a poppet portion, spring means operatively connected with said valve means to cause said sealinG surface to engage said seating surface, said poppet portion including a tapered surface movable within said opening for centering the valve means, said poppet portion also including a shoulder adjacent said tapered surface, said shoulder when the valve is in sealing position being disposed within said opening and adjacent said chamfer, said opening defined by said valve seat means being formed by a substantially straight cylindrical surface, said shoulder comprising a substantially straight cylindrical surface fitting relatively closely within said opening with only a slight clearance between said two substantially straight cylindrical surfaces, said chamber having a predetermined dimension in a direction parallel with the axis of movement of said valve means, said shoulder having a predetermined dimension in a direction parallel with the axis of said valve means which is at least about two times as great as said dimension of the chamfer, said tapered part of the poppet portion being substantially frustoconical in configuration, said valve means including an elongated valve stem, said poppet portion being fixedly supported on said valve stem, and a spring retainer means supported on said valve stem and engaging said spring means.
 2. A valve construction comprising valve seat means, said valve seat means defining an opening for receiving a valve, said valve seat means also including a seating surface, said valve seat means having a chamfer disposed between said opening and said seating surface, valve means including a sealing surface for engaging said seating surface to provide a seal, said valve means including a poppet portion, spring means operatively connected with said valve means to cause said sealing surface to engage said seating surface, said poppet portion including a tapered surface movable within said opening for centering the valve means, said poppet portion also including a shoulder adjacent said tapered surface, said shoulder when the valve is in sealing position being disposed within said opening and adjacent said chamfer, said opening defined by said valve seat means being formed by a substantially straight cylindrical surface, said shoulder comprising a substantially straight cylindrical surface fitting relatively closely within said opening with only a slight clearance between said two substantially straight cylindrical surfaces, said chamfer having a predetermined dimension in a direction parallel with the axis of movement of said valve means, said shoulder having a predetermined dimension in a direction parallel with the axis of said valve means which is at least about two times as great as said dimension of the chamfer, said tapered part of the poppet portion being substantially frustoconical in configuration, a second valve means having a second poppet portion and a second sealing surface, said second poppet portion including a tapered surface for centering the second valve means, a second valve seat means including a second seating surface for engaging said second sealing surface to provide a seal therewith, said first-mentioned sealing surface being formed on said second valve means, said first-mentioned valve means being carried by said second valve means, said second poppet portion having a central opening formed therethrough, said opening receiving said first-mentioned valve means, spring means operatively connected with said second valve means, said spring means being received within said central opening.
 3. A valve construction comprising valve seat means, said valve seat means defining an opening for receiving a valve, said valve seat means also including a seating surface, said valve seat means having a chamfer disposed between said opening and said seating surface, valve means including a sealing surface for engaging said seating surface to provide a seal, said valve means including a poppet portion, spring means operatively connected with said valve means to cause said sealing surface to engage said seating surface, said poppet portioN including a tapered surface movable within said opening for centering the valve means, said poppet portion also including a shoulder adjacent said tapered surface, said shoulder when the valve is in sealing position being disposed within said opening and adjacent said chamfer, second valve means having a second poppet portion and a second sealing surface, said second poppet portion including a tapered surface for centering the second valve means, a second valve seat means including a second seating surface for engaging said second sealing surface to provide a seal therewith, said first-mentioned seating surface being formed on said second valve means, said first-mentioned valve means being carried by said second valve means, said second poppet portion including a tapered surface extending to a point adjacent said second sealing surface and laterally inwardly thereof, said second poppet portion having a central opening formed therethrough, said opening receiving said first-mentioned valve means, spring means operatively connected with said second valve means, said spring means being received within said central opening.
 4. Apparatus as defined in claim 1 wherein said spring means comprises a stable spring.
 5. Apparatus as defined in claim 1 wherein the seating surface on said valve seat means slopes relative to a plane extending perpendicular to the axis of movement of said valve means.
 6. Apparatus as defined in claim 5 wherein said seating surface includes a flat formed thereon adjacent said chamfer.
 7. Apparatus as defined in claim 1 wherein said sealing surface on the valve means comprises a gasket, and gasket retainer means supported on said valve stem and engaging said gasket for holding the gasket in place.
 8. Apparatus as defined in claim 3 wherein said second poppet portion includes a second tapered surface formed adjacent to and laterally outwardly of said sealing surface. 